1. Field of the Invention
The present invention relates to a gas purifier for air pollution control. More particularly, the present invention relates to a gas purifier utilizing the action of a catalyst and the action of a plasma.
2. Description of the Related Art
Air pollution control is a critical social problem. Polluting gases, including toxic components such as COx, CmHn, NOx, and SOx, are exhausted in large quantities from factories and automobiles, and it is important to purify such polluting gases. Also, in a space station, it is necessary to purify a specific gas such as methyl gas.
For air pollution control, large scale gas purifiers such as a centrifugal purifier, a discharge purifier, a desulfurizer, and others are installed in a factory. An exhaust emission control device using a catalyst is mounted in an automobile. These conventional gas purifiers purify gases on the basis of single physical or chemical action, and thus have a limited purification efficiency.
Japanese Unexamined Patent Publication (Kokai) No. 62-33527 discloses a gas purifier comprises a discharge area and a catalytic reaction area located downstream of the discharge area. According to the method described in this publication, exhaust gas is first routed to the discharge area and is ionized to a plasma gas. The plasma gas is then routed to the downstream catalytic reaction area. Also, Japanese Unexamined Patent Publication (Kokai) No. 63-242323 discloses a gas purifier in which gas is treated by a discharge, and the gas is then passed through catalysts.
In the above described Japanese Unexamined Patent Publication No. 62-33527, the discharge area includes needle electrodes to which a voltage of several thousand volts to several tens of thousands volts is applied. In the Japanese Unexamined Patent Publication No. 63-242323, mesh electrodes or bar electrodes and a high voltage generator are used. In this manner, the conventional gas purifier combines the action of a plasma and the action of a catalyst, but needs a high voltage power source to generate a plasma.
In addition, the discharge area and catalytic reaction area are provided as separate stages, and a problem arises that the gas becomes plasma containing gas in the discharge area, but the content of plasma in the gas decreases before the gas reaches the next catalytic reaction area, and the combined effect of an action of plasma and an action of catalyst is not as high as expected.